(1) Field of the Invention
The present invention relates generally to filters and, more particularly, to a filter adapter for a filter vessel utilizing a disposable filter for removing particulate matter from an aqueous flow, especially radioactive materials entrained in cooling water, which reduces exposure to radioactive materials and the volume and weight of the hazardous waste resulting from the end of life of the filter.
(2) Description of the Prior Art
Nuclear reactors use circulating water as a coolant for the radioactive core. Some of the particles picked up by the cooling water are radioactive. Before the water can be recirculated in the cooling loop, the radioactive materials must be removed. This is done conventionally by filter elements that are installed for a given period of time to remove the waste particles. After a period of time, the filter becomes clogged with removed particles and must be replaced.
Conventional filters for this purpose have a perforated, cylindrical stainless steel outer hull or, in some cases, an inner core, and a permanently installed interior filter medium. The filtrate flows through the filter medium and the pores of the stainless steel core.
In addition, many U.S. nuclear plants and some plants in Europe use "Cuno" or similar filter vessels originally designed for non-nuclear applications which normally use baskets or clusters of small filter cartridges rather than a large filter cartridge which may be required to deal with the high flow rates required by a particular application. These baskets of filter cartridges are difficult to handle within a nuclear environment because the disposal of the spent cartridges requires manual human contact. This contact, of course, may result in additional exposure to radiation from the accumulated radioactive waste in most nuclear plant applications.
In an effort to avoid this handling problem, certain adapters have been developed to permit the use of single large filter cartridge in lieu of the numerous small filter cartridges that the Cuno system was designed to use. All of these adapters, such as the Cuno monocartridge adapter and the Pall Will-Fit.TM. adapter, have springs on top of the cartridge and adapter assembly to preload the filter basket to form a seal with the walls of the filter vessel as was used in the original design. The disadvantage of this approach is that because the filter cartridge also must be sealed at its bottom, the cartridge must be sealed in the adapter. Therefore, the filter adapter becomes an expended piece of hardware which must be replaced each time the filter is replaced. Efforts to reuse such adapters have failed because such efforts require as much handling to remove the spent filter cartridges from the adapter as was the case in the original Cuno basket filters.
Thus, there remains a need for a new and improved disposable filter and filter adapter which performs well in existing filter vessels while, at the same time, reduces exposure to radioactive materials and the volume and weight of the hazardous waste resulting from the end of life of the filter.